The purpose of these studies is to examine the effect of 2'-deoxycoformycin and other potent inhibitors of adenosine deaminase on in vitro parameters of human peripheral blood lymphocytic function, and on in vivo parameters of immune function in experimental animals. BIBLIOGRAPHIC REFERENCE: Chassin, M.M., Chirigos, M.A., Johns, D.G. and Adamson, R.H.: Adenosine deaminase inhibitors for immunosuppression. New England J. Med. 296: 1232, 1977.